Caloric dietary components and metabolic hormones can act directly on the brain to influence neural function and relevant behaviors. While several of these signals (e.g. glucose and leptin) are known and studied, the effects of non-caloric dietary components, such as vitamins, are less studied. The fully active form of vitamin D (calcitriol), which functions as a secosteroid, can be derived from dietary vitamin D. The identification of vitamin D receptor (VDR) in dopamine centers in the brain raises the possibility that vitamin D levels can influence these areas. Specifically, it is hypothesized that behaviors affected by dopamine signaling, such as drug addiction, are affected by vitamin D signaling directly to these neurons. Preliminary data suggests that vitamin D levels can regulate gene expression of dopamine signaling genes, as well as behavioral responses to amphetamine, such as locomotor activity and oral consumption. The present application seeks to assess the specific role of VDR activity on these neurons in the context of dopamine release and signaling. Additionally, the potential therapeutic role of exogenous vitamin D will be evaluated in drug addiction paradigms. The proposed work is important for elucidating a novel role for a non-caloric dietary component, while also testing the therapeutic potential of vitamin D for treating drug addiction.